1. Field of the Invention
The present invention relates to a method of recycling useful metals from waste such as wasted flat panel displays, wasted cathode ray tubes, wasted fluorescent tubes, wasted integrated circuits, and wasted printed circuit boards.
2. Description of the Related Art
Recently, regarding display devices for images, etc., a change from the use of cathode ray tubes to liquid crystal display panels or plasma display panels has taken place. Additionally, manufacturing of cathode ray tubes within Japan is not being implemented. Thus, the quantity of wasted cathode ray tubes has increased. Moreover, as far as fluorescent tubes are concerned, it can be presumed that the quantity of wasted fluorescent tubes would increase due to renovations for energy conservation of lightning equipment, changes to apply the same to light-emitting diodes for the future, and the like. In addition, the quantity of integrated circuits and circuit boards used for electronic equipment is increasing. Highly valuable rare earth metals are used for such waste. Such metals include transparent electrodes (ITO: Indium Tin Oxide) comprising a compound of indium oxide (In2O3) and tin oxide (SnO2). Furthermore, many oxides of rare earth metals are used for fluorescent materials in which energy in forms such as ultraviolet light or electron beams is converted into visible light.
Furthermore, cathode ray tubes and fluorescent tubes contain lead (Pb) and antimony (Sb). A large quantity of silver (Ag) is used for electromagnetic shielding meshes for plasma display panels. Also, conventional solders contain lead (Pb) and zinc (Zn). Recent solders that do not contain lead (lead-free solders) contain silver (Ag), tin (Sn), copper (Cu), and the like.
In recent years, it has been difficult to obtain useful metals, including the aforementioned rare earth metals due to speculation and export restrictions of resource producing nations. The necessity for governmental stockpiles has further increased. Therefore, the importance of recycling and recovery of such rare earth metals is growing. Moreover, the demand for metals in developing countries including China has increased. Due to such increase, prices of useful metals, such as silver and copper, are skyrocketing. In particular, accompanying the increase in demand for flat panel displays, an increase in demand for indium (In) is inevitable. Results of computations suggest that even if recoverable reserves are estimated at 6,000 tons at most, indium will disappear by 2019. Research and development for alternative ITO materials, such as zinc oxide, are in progress. However, it is urgently necessary to prolong In resources through recycling. A review of the use of zinc (Zn) in the form of zinc oxide (ZnO) as a constituent of transparent electrode material is also underway. Furthermore, lead (Pb) is used for electrodes of lead acid batteries (secondary batteries) in many cases. Antimony (Sb) is used for aluminum alloy additives, bearing alloys, additives for semiconductors, and the like in many cases.
Recycling of conventional rare earth metals, such as indium, yttrium, europium, lanthanum, terbium, gadolinium, and the like, as well as useful metals, such as lead, antimony, zinc, silver, copper, and the like, is described as follows with reference to the prior patent documents.
(Patent document 1: Kokai (Jpn. Unexamined Patent Publication) No. 2005-334838).
The invention described in patent document 1 mentioned above relates to a recycling system for valuable metals used to collect and recycle indium (In) and silver (Ag) as valuable metals that can be found on panel surfaces as electrode materials from waste of flat panel displays such as liquid crystal display panels, plasma display panels, or the like.
According to patent document 1, as shown in FIG. 1, crushed or scrapped wasted flat panel displays are immersed in HCl solutions. Through filtering such solution, solution containing In and residues containing Ag are separated, and In is extracted. In-containing solution is condensed and is prepared so that prescribed In concentration will take place. Substrates are spray coated with such solution. As a result, clear thin films are formed on the substrates. Additionally, In can be collected by electrolyzing the extracted In-containing solution.
In relation to recovery of Ag, residues containing Ag are immersed in an HNO3 or heated H2SO4 solution. Through electrolyzing and filtering the resultants, a solution containing Ag can be obtained. KCl or NaCl is added to an Ag-containing solution, and AgCl is collected in the form of a solution. Such AgCl solution is heated, and the resulting Ag is collected. Additionally, residues containing Ag are immersed in an HNO3 or heated H2SO4 solution. An Ag-containing solution formed through dissolution and filtering is electrolyzed, and Ag can be collected. Furthermore, Ag-containing residues are immersed in an Na2S2O3 solution. An Ag-containing solution formed through dissolution and filtering is electrolyzed and left to stand, and thereafter Ag2S can be collected.
According to patent document 1, crushed or scrapped wasted flat panel displays are further immersed in an HNO3 solution. Through filtering such solution, a solution containing In and Ag is obtained, residues are separated, and In and Ag are extracted. KCl or NaCl is added and In-containing solutions can be obtained. At the same time, resulting AgCl sediment can be collected. The extracted In-containing solution is condensed and is prepared so that a prescribed In concentration will be attained and substrates are spray coated with such solution. As a result, clear thin films are formed on the substrates. Additionally, In can be collected by electrolyzing the extracted In-containing solution. The collected AgCl solution is thermally treated and is collected in the form of Ag.
(Patent document 2: Kokai (Jpn. Unexamined Patent Publication) No. 2001-296508)
The invention described in the aforementioned patent document 2 relates to a simplified, highly powerful, and economical processing method for wasted liquid crystal display panels, which enables ideal recycling that hardly generates any waste.
According to patent document 2, using fluorescent X-rays, glass substrates for liquid crystal display panels are sorted based on glass type. Organic material contained in liquid crystal display panels is heated and removed. Films formed on the aforementioned glass substrates are mechanically removed and collected in the form of metal powder. Additionally, as a process preceding the process of film removal, glass substrates are crushed and glass chips are recycled as glass materials.
(Patent document 3: Kokai (Jpn. Unexamined Patent Publication) No. 2001-305502)
The invention described in the aforementioned patent document 3 relates to an economical processing method for wasted liquid crystal display panels, which enables ideal recycling that hardly generates any waste.
According to patent document 3, liquid crystal display panels are cut under a state in which polarizing film is present, and liquid crystals are collected. Additionally, following peeling off the polarizing film from the liquid crystal display panels, the corresponding liquid crystal display panels are cut and liquid crystal solution is collected. At this time, glass substrates of liquid crystal display panels are cut without chopping the seal materials encapsulating liquid crystals. A method for dissolution and recovery of liquid crystals using solvents and a method for recovery of liquid crystals by scraping and removing of the same are disclosed.
Recovery of films formed on cut glass substrates is conducted using a method for mechanical detachment and a method for immersing cut glass substrates in concentrated sulfuric acid.
Furthermore, in regards to sorting out types of glass, fluorescent X-rays are used. The sorted glass substrates are then crushed.
(Patent document 4: Kokai (Jpn. Unexamined Patent Publication) No. 2001-305501)
The invention described in the aforementioned patent document 4 relates to an economical processing method for wasted liquid crystal display panels that enable ideal recycling that hardly generates any waste.
According to patent document 4, polarizing film is stripped from liquid crystal display panels and glass substrates of liquid crystal display panels are cut off. Following this process, liquid crystal solution is collected. The cut glass substrates are sorted based on glass type. Thin films formed on the aforementioned glass substrates are mechanically removed and collected. The glass substrates of liquid crystal display panels are cut off without chopping seal materials encapsulating liquid crystals during the process of cutting the panels. Furthermore, following removal of the polarizing film, a method for performing a process for cutting panels is also disclosed. A method of using solvents and a method of scraping of liquid crystals are applied for the recovery of liquid crystals. Fluorescent X-rays are used for determining glass type. As a process preceding the process for thin film removal, a method for crushing the sorted glass substrates based on glass type is used. Thin films on the glass substrates are mechanically removed and collected, and metals such as indium and chromium are collected from the thin films.
(Patent document 5: Kokai (Jpn. Unexamined Patent Publication) No. 2001-337305)
The invention described in the aforementioned patent document 5 relates to an economical processing method for wasted liquid crystal display panels involving the collection and recycling of glass substrates, liquid crystals, and the like, which enables an ideal form of recycling that hardly generates any waste.
According to patent document 5, polarizing film is peeled off from liquid crystal display panels, and glass substrates of liquid crystal display panels are cut off. Following this process, the cut glass substrates are chamfered. The cut glass substrates are sorted based on glass type. Thin films formed on the aforementioned cut glass substrates are removed and collected. Additionally, following performance of polarizing film detachment, a method for conducting a panel cutting process is also disclosed. Furthermore, in the process of cutting panels, a method for cutting the glass substrates without chopping the seal materials encapsulating liquid crystals is also used. Fluorescent X-rays are used for sorting types of glass. In order to remove thin films, a method for etching and/or polishing thin films, and removing organic compound contained in the cut glass substrates is also disclosed. For the purpose of eliminating remaining organic compound, a method for immersing glass substrates in concentrated sulfuric acid or strong alkaline solutions is disclosed. In regards to recovery of liquid crystals, a method for recovery of liquid crystals following the cutting of panels is also disclosed. A method for dissolving liquid crystals using solvents and a method for the scraping of liquid crystals are disclosed. Furthermore, metals such as indium and chromium are collected from the thin films.
(Patent document 6: Kokai (Jpn. Unexamined Patent Publication) No. 2008-103217)
The invention described in the aforementioned patent document 6 relates to environmentally desirable low-cost plasma display panels in which transparent electrodes are formed using ITO alternative materials.
In regards to the invention described in the aforementioned patent document 6, it is disclosed that transparent electrodes, which comprise display electrodes for plasma display panels, are formed using materials mainly based on zinc oxides, and that zinc oxides are used for one of the components of dielectric layers formed to cover the transparent electrodes.
(Patent document 7: Kokai (unexamined patent publication) No. 1997-5514)
The invention described in the aforementioned patent document 7 relates to a color filter for liquid crystal displays in which cracking and peeling are less likely to take place in regards to transparent electrodes for a liquid crystal drive.
In regards to the invention described in the aforementioned patent document 7, it is disclosed that such invention comprises amorphous oxides containing zinc and indium as the main cation elements for transparent electrodes for liquid crystal drives of liquid crystal displays, and that the atomic ratio of the zinc element and indium element, or Zn/(Zn+In), is ensured to be 0.1 or more and 0.2 or less.
(Patent document 8: Kokai (unexamined patent publication) No. 2000-335915)
The invention described in the aforementioned patent document 8 relates to a method for low-cost recovery of glass materials that do not contain impurities such as metals or metal oxides based on low consumption energies and a system thereof.
The invention described in the aforementioned patent document 8 was invented by one of the inventors of the present invention. Wasted glass materials with silicon oxide as a major component that contain metals and/or metal oxides as impurities are dissolved in a hydrofluoric acid aqueous, a hydrofluosilicic acid solution not in a saturated state, or a solution containing fluorine ions that is a mixture of the aforementioned solutions or the like. After a saturated state and a supersaturated state are achieved, additives for supersaturation are added to a solution in which a glass material is dissolved, and oxide silicon is deposited. Additionally, a method for heat treatment of acquired silicon oxide in any one of the atmospheres selected from the group consisting of inert gas, reducing gas, water vapor, mixed gas of inert gas and reducing gas, and mixed gas of inert gas and water vapor is disclosed. Furthermore, a system for recovery of glass materials from wasted glass is disclosed.
(Patent document 9: Kokai (unexamined patent publication) No. 2001-274116)
The invention described in the aforementioned patent document 9 relates to a copper plating solution used to form high-purity copper thin films not requiring special reducing agents. Moreover, the invention relates to a method for forming a copper multilevelwiring structure using the aforementioned the copper plating solution.
The invention described in the aforementioned patent document 9 was invented by one of the inventors of the present invention. A copper plating solution include solution that allows copper ion sources, such as copper oxides and copper hydroxides, to be dissolved and formed in hydrofluoric acid and/or hydrofluosilicic acid. Using such a solution, a multilevel copper wiring structure is formed on semiconductor integrated circuit substrates or multilayer printed circuit boards. Such method is disclosed.
(Patent document 10: Kokai (unexamined patent publication) No. 2004-323931)
The invention described in the aforementioned patent document 10 relates to a copper plating solution that forms copper plating films directly on TaN barrier films, which does not require the formation of copper seed layers or a pretreatment solution for a method involving an electrolyte copper plating solution using acid copper sulfate baths. Additionally, the invention relates to a method for forming a multilevel copper wiring structure using the aforementioned copper plating solution and pretreatment solution.
One of the inventors of the present invention was also one of the inventors of the invention described in the aforementioned patent document 10. A copper plating solution and copper plating pretreatment solution comprise as main components hydrofluoric acids and/or hydrofluosilicic acids including copper ions. At least one member selected from the group consisting of titanium compounds or polyhydric alcohols is added as an additive. Additionally, via an electroless plating method and/or electrolytic plating method, copper plating films are formed directly without forming copper seed layers in advance on various substrates and on barrier metal films comprising TaN films and TiN films. Such method is disclosed. Moreover, a method for conducting electroless copper plating pretreatment and/or electrolytic copper plating pretreatment using an aforementioned copper plating pretreatment solution is disclosed.
(Patent document 11: Kokai (unexamined patent publication) No. 2000-17464)
The invention described in the aforementioned patent document 11 relates to a recycling method whereby, following recovery and regenerating reaction relating to a copper chloride etching waste solution that generates in etching tanks, such solution is again provided for use in plating process, which allows cost reduction for raw materials and reduction of problematic pollution for environmental protection, and an equipment for the same.
According to the aforementioned patent document 11, a copper chloride etching waste solution that generates in etching tanks are collected, copper hydroxide is generated in a sodium-hydroxide solution, and a solid copper oxide is formed based on a pyrolytic technique at a temperature of 80° C. or higher. Subsequently, following dehydration and drying of such solid copper oxide, the resultant is dissolved in sulfuric acid and an ion-containing electrolytic solution is formed. Such solution is transported to plating tanks, and electrodeposition takes place using titanium metal electrode. As such, a recycling method for etching waste solutions is disclosed.
Additionally, according to the aforementioned patent document 11, a recycling equipment for etching waste solution comprising a unit for recovery of copper chloride etching waste solution, a unit for supply of sodium hydroxide, a reaction unit for sodium hydroxide with copper chloride etching waste solution, a dehydrating unit, storage space for dried copper oxide, a dissociation unit, inflow of electrolytic solution and outflow of electroplating residue liquids, and an electroplating unit are disclosed.
(Patent document 12: Kokai (unexamined patent publication) No. 2003-293048)
The invention described in the aforementioned patent document 12 relates to a recycling method whereby great amounts of copper and nickel can be inexpensively recycled from resin plating waste materials through mixing copper plating films and nickel plating films without separating and removing copper components.
According to the aforementioned patent document 12, a method for recovery of metal components from resin plating waste materials is disclosed. Such method comprises a process for forming a metal component enriched mixture that enhances the percentage of existing plating film components of resin plating waste materials with copper plating films and nickel plating films formed on surfaces of resin substrates, and a process for recovering metal components that acquire alloys containing copper and nickel following heating and dissolution regarding the aforementioned mixture. In relation to the process for forming a metal component enriched mixture, a method for reducing the aforementioned resin substrate components, a method for increasing the aforementioned metal components, and a method for reducing the aforementioned resin substrate components and increasing the aforementioned metal components are provided. According to the aforementioned patent document 12, in regards to the method for recovery of metal components, alloys such as Cu—Ni alloys and Al—Cu—Ni—Cr alloys can be obtained.
(Patent document 13: Kokai (unexamined patent publication) No. 2000-348698)
The invention described in the aforementioned patent document 13 relates to a valve-regulated lead acid battery that allows the number of processing steps to be reduced at the assembly and is superior in terms of separation and recovery at the time of recycling, and a method of manufacturing the same.
In regards to the invention described in the aforementioned patent document 13, a method for manufacturing a valve-regulated lead acid battery with the application of a silane coupling agent solution to the surface of bolt casts and drying the same, inserting such bolt casts into resin materials and shaping the same, and fabricating a lid therefor is disclosed.
(Patent document 14: Kokai (unexamined patent publication) No. 1997-157767)
The invention described in the aforementioned patent document 14 relates to a method for lead separation that separates lead from specimens that include lead and makes it easier to dispose of and recycle the specimens.
In relation to the invention described in the aforementioned patent document 14, it is disclosed that lead from lead solder is separated using hydrochloric acid, acetic acid, and the like, solvents of methanol, ethanol, ethylene glycol, and the like, and lead-separating liquids prepared through dissolution of iodine. It is also disclosed that components are nondestructively separated and recovered via such method.
[Non-patent document 1] Ken Nara, Hidemitsu Sasaki, Daisuke Yamaguchi, Michiru Sugawara, Yu Nishimura, Tetsuya Homma, and Hideo Takahashi: “Evaluation of Metal Element Separation Performance from Wasted Silicate Glass Materials” Abstract for Speech of the 65th Academic Lecture of the Japan Society of Applied Physics, presentation number 3p-E-8, p. 354, Sep. 3, 2004
The aforementioned non-patent document 1 relates to a conference presentation involving one of the inventors of the present invention. Results based on research concerning the possibility of separation of metal elements through a cyclic voltammetry method are disclosed. Lead oxide (PbO) and iron oxide (III) (Fe2O3) are each dissolved in separate hydrofluoric acid (HF) aqueous solutions. Platinum (Pt) is used for electrolysis. Results based on research concerning current-voltage characteristics involving the use of a cyclic voltammetry method are disclosed. When wasted silicate glasses are dissolved in an HF solution and the resultant is prepared by hydrofluosilicic acids, there is a high possibility of being able to separate Pb and Fe in the forms of PbF2 and Fe2O3, respectively. [Non-patent document 2] Hidemitsu Sasaki, Daisuke Yamaguchi, Yu Nishimura, Ken Nara, and Tetsuya Homma: “Evaluation of Metal Element Separation Performance from Wasted Silicate Glass Materials (2)” Abstract for Speech of the 52nd Meeting of the Japan Society of Applied Physics and Related Societies, presentation number 30a-YA-2, p. 498, Mar. 30, 2005
The aforementioned non-patent document 2 relates to a conference presentation involving one of the inventors of the present invention. Fluorinated silicon oxide (SiOF) thin films are formed using a solution whereby glass powder with the same composition as CRT glass is dissolved in a hydrofluoric acid (HF) aqueous solution. Results of performance concerning characterization are disclosed. Silica (SiO2), lead oxide (PbO), barium oxide (BaO), strontium oxide (SrO), and the like are prepared based on the same composition as CRT glass, and the resultants are dissolved in an HF solution resulting in. A hydrofluosilicic acid (H2SiF6) aqueous solution, and then, a supersaturated additive Al is added, and silicon substrates are immersed. SiOF thin films are then deposited.